Generally, reflecting solar troughs are made of shiny metal sheets which are backed by supporting ribs. Primarily because of manufacturing limitations at the mill, there are necessarily restrictions on the areas of the sheets. Consequently, a multiplicity of reflectors are often required for a given solar energy project. As a rule, the sheets with rigid supporting ribs, are assembled at plant site because of the difficulty and expense in attempting to assemble the sheets and ribs in the field. As a result, the mirrors are heavy and bulky and difficult to ship, adding further costs to the finished product.